The goal of this contract is to provide support of National Toxicology Program (NTP) hazard assessment activities targeted toward the prevention of diseases or adverse effects caused by environmental exposure to chemical or physical agents. This contract provides statistical, biomathematical, and computational expertise and resources to summarize, analyze, and aid in the interpretation of data from various NIEHS experimental studies. These studies consist of carcinogenesis bioassays and toxicology studies carried out by the National Toxicology Program (NTP), and laboratory and methodological investigations carried out by the Division of Intramural Research (DIR). In support of the NTP's two-year bioassays, Constella has responsibility for developing, maintaining, and upgrading statistical software for the Toxicology Data Management System (TDMS). This software includes programs for statistical analysis of tumor incidence, non-neoplastic lesion incidence, body weight, survival, food and water consumption, and programs for producing camera ready plots of body weight and survival estimates. In support of NTP toxicology studies, Constella provides dose-response analyses of toxicity endpoints for use in NTP Technical Reports. Toxicity endpoints include organ and body weights, survival, clinical chemistry, hematology, and histopathology observations. Constella also conducts statistical analyses of data from NTP's Reproductive Assessment by Continuous Breeding Program. These analyses involve measurements of fertility, sperm morphology, vaginal cytology, and litter data. Constella also conducts toxicokinetic modeling of selected chemicals. These models go beyond the statistical analysis in that they can be used to make physiology based predictions. As part of its support of NTP, Constella is responsible for maintaining historical databases for tumor incidence in control animals from two-year bioassays and for toxicity endpoints from short-term toxicity and reproductive studies. Constella summarizes the tumor incidence database annually and makes the results available to NTP in electronic and hardcopy formats. Toxicity and reproductive databases are updated continuously and summarized at the request of NTP scientists. Constella conducts statistical analyses for validating alternative tests being considered as replacements for existing animal tests, as requested by the NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM). In support of the Division of Intramural Research (DIR), Constella provides statistical consulting expertise, analysis of experimental data, statistical support for human studies, and computational support for experimental and methodological research. In collaboration with NIEHS scientists, Constella provides statistical support for laboratory research by aiding in the design and interpretation of laboratory experiments, by providing statistical computations, and by summarizing and displaying experimental data for peer-reviewed publication. Constella also supports methodological research of importance to DIR by investigating properties of alternative statistical procedures by computer simulation and by supplying theoretical and computational support for biomathematical research efforts. Keywords NTP;TDMS;biometrics;Oracle;Data analysis;biostatistics;experimental design;statistical computing;National Toxicology Program;toxicokinetic models;cancer bioassays;reproduction;biomathematical modeling;bioinformatics.